MakeContextCurrent before querying for swapbuffers_complete GL extension
MakeContextCurrent before querying for swapbuffers_complete GL extension

RenderViewImpl::SupportsAsynchronousSwapBuffers() makes GL calls without calling makeContextCurrent(). This used to work,
but with http://trac.webkit.org/changeset/106700 single-threaded context creation no longer does an implicit makeContextCurrent()
so this fails DCHECKs in the command buffer code.

BUG=none
TEST=can instantiate compositor in debug mode at WebKit rev >= 106700

Review URL: https://chromiumcodereview.appspot.com/9317105

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@120455 0039d316-1c4b-4281-b951-d872f2087c98

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